Preparation of 1, 3-diamino-2, 4, 6-trinitrobenzene



United States Patent F 3,278,604 PREPARATION OF 1,3-DIAMINO-2,4,6- TRINITROBENZENE Joseph Adrian Hoffman, Bound Brook, N.J., and Charles Franklin McDonough, Youngstown, Ohio, assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed July 16, 1963, Ser. No. 295,538 5 Claims. (Cl. 260-581) This invention is concerned with an improved process for the preparation of dimethoxytrinitrobenzene and with the conversion thereof to diaminotrinitrobenzene of general utility as a high energy material.

For convenience in referring thereto in the following discussion, the long chemical names dimethoxytrinitrobenzene and diaminotrinitrobenzene are abbreviated as DMTB and DATB respectively. Use of these abbreviations also simplifies maintaining the distinction there between.

Industrial chemistry is encountering a constantly increasing demand for so-called high energy materials which are coming into use in a continually enlarging number of fields. DATB is one such typical material. Consequently there is a need for an industrially-suitable method for its preparation.

Chemically, one practical method of preparing DATB is by sulfonation of 1,3-dimethoxybenzene and subsequent nitration of the resultant sulfonate to DMTB. This is followed by conversion of the DMTB to the desired DATB by reaction with ammonia. This is illustrated in the following reaction scheme.

OCH; Hm-

OaN NO: OrN N02 This method does have potential commercial possibilities. However, the method involves a number of procedural difficulties andproblems. These are found especially in the preparation of the DMTB. Serious difficulties are encountered, especially in larger scale opera tions, during nitration and subsequent DMTB isolation. The nitration mixture thickens and foams, making it almost impossible to attain proper mixing during nitration or to isolate the DMTB. In attempting to overcome the difiiculties, use of relatively larger volumes of sulfuric and nitric acids was proposed. However, this proposal did not prove entirely satisfactory and the thickening and foaming problems were not adequately solved.

Consequently, the need still exists for an improved method to make it more useful with respect to ease of operation; material handling, increased yield and better material recovery. It is, therefore, a major object of the present invention to develop a procedural operation which is not subject to these drawbacks. This object has been accomplished to a surprisingly successful degree by a modified operation based on the discovery that if nitration is carried outor completed in the presence of a suitable inert organic solvent, or. if the reaction mixture is thoroughly contacted with the solvent, the principal difficulties of the previous method are overcome.

Normally, nitration is carried out in two steps, in the 3,278,604 Patented Oct. 11, 1966 "ice first, effecting sulfonation by reaction with sulfuric acid, followed by conversion to the DMTB by reaction with concentrated nitric acid. The solvent may be added to the reaction mixture at various points. Thus it may be added after sulfonation is complete but before nitration, or it may be added after nitration is complete. However, the preferred practice is to add the solvent in portions; adding at least one portion after sulfonation but before nitration, and adding the remainder after nitration is complete but before isolation of the intermediate.

During nitration it is preferable that sufficient solvent be available to maintain easy stirability during the nitration. However, it is preferable also to have sufficient solvent present after nitration so that all of the DMTB is extracted into the solvent phase. In this way, the DMTB is removed from the reaction area and may be easily isolated by evaporation of the solvent.

Although the choice of solvents which are operable is limited, several have been found practical for the purpose. Nitrobenzene is one which has been found operable. Others are alkylene halides having not over two carbon atoms in the alkylene group. Methylene chloride and ethylene chloride are perhaps the most desirable, particul-arly if the DMTB isto be completely isolated.

The superior results obtained using an alkylene chloride such as methylene or ethylene chloride and nitrobenzene are rather surprising since it could not have been expected that such solvents would be so effective. Seemingly closely related solvents such as chloroform, perchloro ethylene, carbon tetrachloride, chlorobenzene and trichloroethylene do not produce satisfactory results.

While in the foregoing discussion isolation of DMTB has been discussed as a normal operation, this was true of the previous procedure. It is a special advantage of the process of the present invention that prior to the preparation of the DATB, the DMTB intermediate need not be isolated. Amination using ammonia may be carried out directly on the nitration product in the solvent solution in which it is made. This obviates the step of removing the solvent for isolation of the intermediate. However, if so desired in the conversion to DATB, the DMTB intermediate still may be isolated, dried and then converted to the final diarnine product.

In effecting amination of the intermediate in solution, it is desirable to react with an excess of ammonia. This may be done by treating the extract directly with gaseous ammonia. However, the ammonia is more conveniently handled when dissolved in a solvent such as methanol which is miscible with the alkylene chloride. A convenient method involves the reaction of 30% aqueous ammonia in a large volume of methanol with a solution of the nitro intermediate in a solvent.

By use of the process improvement of this discovery, a superior method results for the preparation of 1,3-dimethoxy-2,4,fi-trinitrobenzene and for the corresponding 1,3-diamino derivative.

The many advantages of the present process include greater ease of handling and reduced labor requirements; elimination of objectionable thickening and foaming during nitration; a considerable reduction in reaction volume, making it possible to use smaller equipment and therefore less capital expense for a desired production capacity; reduction in the amount of nitric acid used; removal of exothermic effects by refluxing solvent; elimination of the isolation and subsequent drying of the intermediate nitro compound; purer product more easily obtained; and, since a drowning step is avoided, possible recovery of spent acid in undiluted form making for increased ease of rectification.

The sulfonation and nitration steps are carried out under conventional conditions using at least an excess of the sulfonation and nitration reactants. Because of the activating effects of the ni-tro groups, the amination reaction for replacement of the methoxy radicals with amino radicals by reaction of ammonia, proceeds very easily at room temperature.

As pointed out above, the solvent, such as methylene chloride, may be added after sulfonation is complete but before the nitration is carried out. While the solvent may be added after the nitration, it is preferable to add at least a portion of the agent before or during nitration, to enable improved stirring and removal of the product. However, for the most convenient operation, it is desirable to add a portion of the agent before nitration starts. The remainder is then added after nitration is complete. One additional point should be noted. When nitration is carried out in the presence of the agent, the nitration reaction is usually slightly slower and somewhat more time should be allowed for completion of the reaction.

Before isolation of the nitro intermediate and/or its conversion to the diamino derivative, it is preferable to wash the methylene dichloride or nitrobenzene solution of the intermediate with an alkaline material such as sodium hydroxide solution or sodium carbonate solution. This removes traces of acid, but more important it removes any phenolic bodies, which for the most part, are the only by-products of the reaction. The solution of l,3-dimethoxy-2,4,6-trinitrobenzene, at this point, is very high in purity. This is evidenced by the color and higher melting point of diamino trinitrobenzene prepared from said solution as compared to the diamino trinitrobenzene prepared by the former procedure.

The invention will be further illustrated by the following examples. Therein, unless otherwise noted all parts and percentages are by weight and all temperatures are in degrees Centigrade.

Example 1 To 460 parts of 95% sulfuric acid was added 43.1 parts of 1,3-dimethoxybenzene; addition being carried out rapidly with stirring. The mixture is then heated at 90 to 95 C. for about one-half hour, followed by cooling to about 15 C. To the resultant mixture was added 136 parts of 70% nitric acid with constant stirring and at such a rate that the temperature did not exceed 30 C. After about 60-65% of the nitric acid had been added, the mixture suddenly thickened to such consistency that it became difiicult to stir and proper mixing was not possible. Some of the material deposited on the walls of the reaction flask. After nitric acid addition had been completed, the mixture was stirred as well as possible for another half hour. To this mixture was then added 800 parts of methylene chloride; after a short period of stirring at room temperature all the solid material disappeared and passed into the organic solvent phase. The methylene chloride phase was separated and washed with cold sodium hydroxide solution. The washed solution was added to a solution of 860 parts of methanol and 80 parts of 29% aqueous ammonia solution. Addition was carried out rapidly at room temperature; and was-followed by stirring for an additional half hour. Resultant solid product was isolated by filtration, washed with methanol and dried. A 75% yield of DATE (56 to 57 parts) was obtained.

Similar results are obtained when ethylene chloride is substituted in the above process for the methylene chloride in equivalent volume.

Example 2 The procedure of Example 1 was followed except that 130 parts of methylene chloride was added to the mixture after the sulfonation but before the addition of the nitric acid; and 670 parts of methylene dichloride was added after the nitration step was complete. The ammonolysis reaction and isolation were carried out as described in Example 1, giving a 72% (55 parts) yield of product.

In the above run the mixture is easily stirred throughout the nitration procedure and no thickening is observed. Similar runs were carried out on larger scale of three times the amount and nine times the amount shown in Example 2 with substantially the same results.

Example 3 735 parts of dimethoxybenzene (0.053 mol) was added rapidly to 4200 parts by volume of concentrated sulfuric acid, 97% while actively' stirring. The mixture was heated at about 95 C. for 30 minutes; then cooled to about 5. Nitric acid (70%) 1500 parts by volume was added with stirring and at such a rate that the temperature of the mixture did not exceed 30 C. When addition of the acid was complete, the mixture 'was stirred for 30 minutes. Nitrobenzene, 7500 parts by volume was added at one time, and the mixture stirred rapidly for 5 minutes. The nitrobenzene extract was separated from the spent acid and then washed with 10,000 parts of cold 5% sodium hydroxide. The washed extract was added directly to a solution of 18,000 parts of methanol and 1000 parts of 29% aqueous ammonia. The mixture was stirred for 30 minutes and filtered. The DATB was washed with methanol and dried in a vacuum oven. The yield was 9800 parts.

Example 4 For purposes of comparison and to illustrate the previous practice using no solvent the following procedure was carried out. To 7700 parts of 95% sulfuric acid was added 735 parts of 1,3-dimethoxybenzene. The stirred mixture was heated to to C. for 30 minutes and then cooled to 5 to 10 C. Then 4000 parts of 70% nitric acid was added slowly at such a rate that the temperature would not exceed 30 C. The mixture was then stirred for 15 minutes. Stirring became extremely difficult and the mixture was very diflicult to work. It was then poured onto an excess of a mixture of ice and water; the intermediate solid product was removed by filtration, washed with water and then dried. A solution of 1200 parts of the above intermediate in 6300 parts of benzene was then added gradually to a solution of 800 parts of 30% aqueous ammonia in 14,500 parts of methanol. The final mixture was stirred for '30 minutes and the solid product is then isolated by filtration, washed with methanol and dried giving the DATB product with a MP. of 284 C. The overall yield was about 75 We claim:

1. In the process for preparing 1,3-diamino-2,4,6-trinitrobenzene from 1,3-dimethoxy benzene comprising the steps of (1) reacting the 1,3-dimethoxy benzene with concentrated sulfuric acid to form 1,3-dimethoxy-2,4,6-trisulfobenzene, (2) reacting the l,3-dimethoxy-2,4,6-trisulfobenzene with concentrated nitric acid to form 1,3-dimethoxy-2,4,6-trinitrobenzene and (3) reacting the l,3-dimethoxy-2,4,6-trinitrobenzene with ammonia to form the 1,3- diamino-2,4,6-trinitrobenzene; the improvement which comprises conducting nitration step 2 in the presence of a solvent for the l,3-dimethoxy-2,4,6-trinitrobenzene, said solvent being selected from the group consisting of nitrobenzene and an alkylene chloride of less than 3 carbon atoms, whereby said 1,3-dimethoxy-2,4,G-trinitrobenzene product is extracted into the solvent phase, separating the solvent phase from the reaction mixture and reacting the 1,3-dimethoxy-2,4,6-trinitrobenzene in said solvent phase with an excess of ammonia to convert the 1,3-dimethoxy- 2,4,6-trinitrobenzene to 1,3-diamino-2,4,6-trinitrobenzene and filtering off the resulting solid 1,3-diamino-2,4,6-trinitrobenzene product. p

2. A process according to claim 1 wherein said solvent agent is methylene chloride.

3. The process of claim 1 wherein the 1,3-dimethoxy- 2,4,6-trinitrobenzene in the solvent phase is reacted with aqueous ammonia.

5 4. A process according to claim 1 wherein said solvent agent is ethylene chloride.

5. The process of claim 1 wherein the 1,3-dimethoxy- 2,4,6-trinitrobenzene in the solvent phase is reacted with gaseous ammonia.

References Cited by the Examiner UNITED STATES PATENTS 1,325,168 12/1919 Perruche 260645 2,826,611 3/1958 Fischback et a1. 260-688 X 10 2,970,171 1/1961 Cryer et a1 260-581 3,002,998 10/1961 Kaplan et a1 260581 3,100,797 8/1963 Harris et a1 260-688 X 6 OTHER REFERENCES CHARLES B. PARKER, Primary Examiner.

DALE R. MAI LANAND, ROBERT V. HINES,

Asszistant Examiners. 

1. IN THE PROCESS FOR PREPARING 1,3-DIAMINO-2,4,6-TRINITROBENZENE FROM 1,3-DIMETHOXY BENZENE COMPRISING THE STEPS OF (1) REACTING THE 1,3-DIMETHOXY BENZENE WITH CONCENTRATED SULFURIC ACID TO FORM 1,3-DIMETHOXY-2,4,6-TRISULFOBENZENE, (2) REACTING THE 1,3-DIMETHOXY-2,4,6-TRISULFOBENZENE WITH CONCENTRATED NITRIC ACID OF FORM 1,3-DIMETHOXY-2,4-6-TRINTRIOBENZENE AND (3) REACTING THE 1,3-DIMETHOXY-2,4,6-TRINITROBENZENE WITH AMMONIA TO FORM THE 1,3DIAMINO-2,4,6-TRINITROBENZENE; THE IMPROVEMENT WHICH COMPRISES CONDUCTING NITRATION STEP 2 IN THE PRESENCE OF A SOLVENT FOR THE 1,3-DIMETHOXY-2,4,6-TRINITROBENZENE, SAID SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF NITROBENZENE AND AN ALKYLENE CHLORIDE OF LESS THAN 3 CARBON ATOMS, WHEREBY SAID 1,3-DIMETHOXY-2,4,6-TRINITROBENZENE PRODUCT IS EXTRACTED INTO THE SOLVENT PHASE, SEPARATING THE SOLVENT PHASE FROM THE REACTION MIXTURE AND REACTING THE 1,3-DIMETHOXY-2,4,6-TRINITROBENZENE IN SAID SOLVENT PHASE WITH AN EXCESS OF AMMONIA TO CONVERT THE 1,3-DIMETHOXY2,4,6-TRINITROBENZENE TO 1,3-DIAMINO-2,4,6-TRINITROBENZENE AND FILTERING OFF THE RESULTING SOLID 1,3-DIAMINO-2,4,6-TRINITROBENZENE PRODUCT. 